Nematic liquid crystals (LCs) are one-dimensionally ordered fluids commonly formed by rod-shaped molecules. Dispersed colloidal particles disrupt the nematic order, and minimization of the elastic energy leads to the formation of anisotropic colloidal structures.1 Sufficiently large particles, depending on the strength and direction of the nematic anchoring on the particle surface, can form various types of topological defects such as Saturn rings, hyperbolic hedgehogs, and boojums in agreement with theoretical considerations.2-7 Past experimental studies focused on dispersions of water microdroplets,1,8,9 ferro-fluids,10 gold coated glass spheres,11 or silicon oil12-15 in nematic LCs (N-LCs) as well as latex particles in lyotropic LCs.9,16 For most particles, if the nematic LC molecules are strongly and perpendicularly anchored at the surface of a spherical particle, the particles act like a radial hedgehog carrying a topological charge. Placed in a uniformly aligned nematic solvent to satisfy the boundary conditions at infinity, the particle should nucleate a further defect in its nematic environment. As theoretically predicted,17,18 the dipole is the preferred configuration for large particles and sufficiently strong anchoring, although quadrupoles are also observed.11 The topological dipole formed by one quasi-spherical particle and an accompanying topological defect, known as a hyperbolic hedgehog, generate elastic forces that lead to the formation of chain-like particle aggregates.19 However, the interactions between colloidal particles and the nematic LC molecules strongly depend on the particular combination of the two materials, the molecular structure and elastic properties of the LC, as well as on the type and likely the size and shape of the colloidal particle used.
Recent theoretical studies on the structural properties of gold nanoclusters have shown that the most stable (lowest energy) isomers of bare Au28, Au55 as well as thiol-protected clusters (e.g., Au28(SCH3)16) correspond to chiral nanostructures.20 These findings provide support for the existence of chirality in noble metal clusters suggested by the intense optical activity measured in the metal-based electronic transitions of size-separated glutathione-protected gold particles in the size range of 20 to 40 atoms.21 Further theoretical work, based on quantifying chirality via the Hausdorff chirality measure (HCM),20,22,23 predicts that strong structural distortions in a gold cluster upon thiol protection could, for example, induce chirality in an achiral unprotected cluster.20 
In addition to the work of Whetten et al. on glutathione capped gold nanoparticles,21 the groups of Fujihara and Yao reported, for example, on the syntheses of optically active nanoclusters protected with chiral (R)- and (S)-BINAP24 or penicillamines25 (D-Pen, L-Pen, and racemate). It is important to note that all three groups used enantiomeric species of the capping agent for the synthesis of their gold nanoparticles resulting in enantiopure particles with an optical activity that is easily identified by circular dichroism (CD) spectroscopy. However, it appears that none of the considerably complex CD spectra in the UV regions, the CD signals at wavelengths where the used protecting agent does not absorb as well as an inversion of the ellipticity, and θ (mirror image) from free capping agent to the capped nanocluster25 can not be explained by the chirality of the capping agent itself. Hence, the structured CD spectra are likely due to the quantized electronic transitions and their interactions in the cluster, which indicates, as theory predicts,20 that nanoparticles can indeed form well-defined stereostructures as ‘normal’ chiral molecules do.
Circular Dichroism is observed when optically active matter absorbs left and right handed circularly polarized light with a different absorption coefficient. Another sensitive probe for molecular chirality are liquid crystalline phases, in particular the nematic phase. Nematic liquid crystals are one-dimensionally ordered fluids commonly formed by rod-shaped molecules. It has been known for a long time that doping nematic phases with chiral, nonracemic compounds (chiral additives or dopants) transforms them into chiral nematic phases,26 characterized by a helical spatial arrangement of the director. In this chiral structure, the anisotropic molecules rotate in a helical manner to form lamellae of equally spaced planes with a common molecular orientation. Polarizing optical microscopy (POM) commonly provides direct evidence of the chirality induced by a chiral dopant in a non-chiral nematic liquid crystal. Characteristic textures and defect structures clearly reveal the difference between chiral and non-chiral nematic phases. Depending on the boundary conditions (planar, homeotropic), between crossed polarizers nematic liquid crystals such as Felix-2900-03 usually produce so-called Schlieren (FIG. 1), marble or thread-like textures, whereas the chiral nematic phase induced by doping 5 wt % of a chiral dopant such as (S)-Naproxen into Felix-2900-03 can display so-called oily-streak, fan-like, fingerprint (FIG. 2) or cholesteric finger textures.27 